Shock

O2 Delivery (DO2)

• O is delivered to tissues to maintain normal aerobic metabolism – DO ~ 900–1100 mL/min (normal).

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• O delivery to tissues is determined by cardiac output × content of O in the arterial blood.

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DO 2 = CO x CaO2

Oxygen Consumption (VO2)

VO2, tissue oxygen consumption:

– ~ 200–270 mL/min (normal)

– determined by:

• metabolic demand (most important) – e.g. increased in sepsis
• tissue ability to extract oxygen from arterial blood
• oxygen delivery, especially when this is very low.

Relationship between O2 consumption and O2 delivery is the O2 extraction ratio (ERO2)

– Normally, the body extracts 25% of the oxygen that is delivered

– The rest goes back to the heart